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When I Debug my WPF Project Visual Studio runs the wrong Project/Is just blank

When i hit F5, for some reason visual studio runs a blank WPF application. And when i hover over the application in the task bar the application name is the name of a different project of mine. Please if you know how to fix this tell me as it is just slowing my everything down for me. Thanks.

You can try to open the task manager and close all debug programs(Task Manager /Processes/*.vshost.exe *32").

I am not sure I understood, because I think you have a duplicate name problem, or in any case, if the other project is empty, try to delete it, and then try to put the project you want to run as a startup project like this,:
Right click on the project in the solution Explorer --> Set up as a start up project

Unable to access 'Build Action' property for .cs files

i got a problem with my site with my app_code files and a lot of question ive read people say you need to change the proprties of the .cs files to Build Action.
by right clicking the .cs files and press proprties.
but...
when i right clicking the files i cant see any option called proprties so i press F4 and it open a proprties window and i just click on the .cs file and still cant see any option i can change somthing to Build Action.
any idea why i cant see this options?
EDIT:
my problem is that when i get in the file proprties i have only 2 options...
thay are called:
1.Full Name
2.Full Path
EDIT2:
here what i see in visual studio 2010 when i try access the protrtie menu/window
http://img338.imageshack.us/img338/2359/blac.png

As Microsoft points out in the article "Web Application Projects versus Web Site Projects":
Web application projects use Visual Studio project files (.csproj or
.vbproj) to keep track of information about the project. Among other
tasks, this makes it possible to specify which files are included in
or excluded from the project, and therefore which files are compiled
during a build.
An answer to a similiar question at CodeProject's forums reveals a hint. Abstract:
[...] Looks like you are working on a web application that is actually a
Website as per Visual Studio. You would need to create a new Web Application
and probably copy over the source files there. [...]
http://www.codeproject.com/Questions/173637/Setting-Build-Action-for-Files-in-App_Data

Have you tried this:

You say you haven't got the option being suggested by other posters.
If this is the case, than it is quite possible that your Visual Studio settings are corrupt; this can give rise to all sorts of odd behaviour.
I would suggest you reset your settings, but please be aware you will lose any custom IDE settings that you've previously applied.
Try this:
In Visual Studio, go to Tools->Import and Export Settings
Choose "Reset All Settings" and click Next
Choose to save your current settings if you wish, or select "no" and then click next.
Choose the collection of settings( he IDE preset) you want, probably "Visual C# Development Settings"
Visual Studio will now revert all settings. Hopefully this will make the Build Action reappear.
[EDIT]
It might be worth trying safe mode too.
To do this, start up a "Visual Studio Command Prompt" from your start menu/programs list in Windows, and start Visual Studio with
devenv.exe /SafeMode
Does this make the options appear?

You can copy the file from Windows Explorer and paste it in the Solution Explorer. It will replace (or do nothing but incorporating it in the proj file) the file and recognize it as C#.

Normally you should see a Property named "Build Action" in the first line of the Property Window. This property should be set to "Compile".

Please select file and right click on it so that you will get following screen
Than click on the Properties you will get following screen
You can find build option in as a first option.

Visual Studio. Code changes don't do anything

Any changes I make to my code aren't doing anything. I've even tried putting lines in that I know will crash my program, and nothing. It just keep running the old version. It's even loading old versions of files I've edited and saved.
There a 3 projects in my solution. 2 are pure C#. 1 is a WinForms application.

It sometimes happens that some files "are being used by another process".
Close your solution and delete all "bin" and "obj" subfolders of all your projects that are included in the solution.
Then open your solution again, execute "Clean solution" and build it again.

Check this setting in Tools/Options, then under Projects and Solutions>Build and Run.
On Run, when build or deployment errors occur:
My personal preference is for this value to be 'Do not launch'. It will prevent Visual Studio from launching the "last successful build".

Try Ctrl+Shift+B. This will build your solution (not just a particular project). Other environments might build when you save but this needs to be explicit in Visual Studio.

Had issue with saving code changes on VS2017 (mac) Version 7.3 Preview (7.3 build 740)
Only way to get file changes to save was to do File > Save All
Doing File>Save would act like the file saved. But, when I opened the file again and no changes were saved.

Ok, you need to add more detail, but you may want to have a look at this answer:
How to enable/disable compile errors warning in Visual Studio

delete Published DLL From Bin
file names -
projectName.ddl
projectName.pdb
delete these two files and run project

I had the same problem (Visual studio 2015 is not noticing my modifications in C# XAML files).
Problem solved by deleting 2 'debug' subfolders. One in the bin folder and one in the obj folder.

I met the same problem. the code changes is not saved.(you can see from the edit it is in Yellow color. e.g. indicating changes). SAVE and BUILD will not let it save the changes. i have to wait sometime, then it could possibly save success..

Deleting the whole project and the corresponding folder from local and check out the solution again. This worked for me=> VS2017

I solved the problem like this:
1. I closed the program
2. I opened the folder that contains the file (.csproj) and opened it with Visual Studio.
Next, I chose the folder to run the command as in the image

Had the same problem. Turns out I had moved a project folder. Even when opening the solution from the moved folder and editing and saving this source code, VS 2019 was building and running a different instance of the program with the same name. Go to File-> Save yourproject.cs as..and manually walk back through the directory structure to find the instance VS is actually running. Hope this helps.

also check another option in Tools>Build and Run>Only build startup project & dependencies if you have more than 1 nested dependency, especially when using Prism or any other reflection-based frameworks that prevent "dependency detection". Also, make sure you're in the editor when using shortcuts like Ctrl+S (Save) or Ctrl+Shift+S (Save all)

Go to this location:
C:\Users\<your_system>\AppData\Local\Microsoft\VisualStudio\<studio_version>
Then remove all files and start Visual Studio.

this was the error , no changes made after build.

Unable to copy a file from obj\Debug to bin\Debug

I have a project in C# and I get this error every time I try to compile the project:
(Unable to copy file "obj\Debug\Project1.exe" to "bin\Debug\Project1.exe". The process cannot access the file 'bin\Debug\Project1.exe' because it is being used by another process.)
So I have to close the process from the task manager. My project is only one form and there is no multi-threading.
What is the solution (without restarting VS or killing the process)?

This should work.
Go to your project properties.
Inside Build Events, under Pre-build event command line, add these two lines of code:
if exist "$(TargetPath).locked" del "$(TargetPath).locked"
if exist "$(TargetPath)" if not exist "$(TargetPath).locked" move "$(TargetPath)" "$(TargetPath).locked"

#Udpate: Since the time I was first posting this 'answer', I tend to another explanation to the problem. The issue since than happened more and more often outside of Visual Studio also - while trying to copy an .exe file from one folder to another. While in the first place Windows did not allow to copy(!) an .exe file (it was first asking me for administrative rights but refused to copy it afterwards anyway) it still showed up in the explorer. But after a while - without any further action taken, it disappeared magically. Just like the problem in the question always seems to solve itself after a while. So i assume, the problem is more related to a delayed deletion of the project output file and less a buggy VS. I apologize for any unjustified suspicion. :|
This gives the search for a solution a complete different direction, I guess. Did find that link and will update on any progress:
https://superuser.com/questions/234569/windows-7-delayed-file-delete
========================================================================
This is a known bug in VS. I discovered it very often - mostly in VS2010 (with/without SP1). Several "solutions" are recommended. Some of them, which kind of helped for me:
Delete the .suo file in your project dir. Eventually need to create your whole solution from scratch.
Close any Windows Form Designers may remain open.
Use a prebuild script, which deletes the target from the output dir.
Disable the VS hosting process.
None of these really fixes the bug. But it may brings the VS back to a usable state - until a true solution is provided by MS (if ever will).
http://social.msdn.microsoft.com/Forums/en/vsdebug/thread/cea5e4b2-5b33-453c-bffb-8da9f1a1fa4a
http://social.msdn.microsoft.com/Forums/en/vbide/thread/cd12f3c7-de96-4353-adce-23975e30933f

I can confirm this bug exists in VS 2012 Update 2 also.
My work-around is to:
Clean Solution (and do nothing else)
Close all open documents/files in the solution
Exit VS 2012
Run VS 2012
Build Solution
I don't know if this is relevant or not, but my project uses "Linked" in class files from other projects - it's a Silverlight 5 project and the only way to share a class that is .NET and SL compatible is to link the files.
Something to consider ... look for linked files across projects in a single solution.

This is happening because [yourProjectName].exe process is not closing after finishing debugging.
There are two solutions to this problem.
Every time you make change to application, Go to Task Manager -> Processes -> [yourProjectName].exe, end this process. You have to end this process every time you make changes to system.
Add a exit button in your application to exit window and add these line to click event
System.Diagnostics.Process.GetCurrentProcess().Kill();
Application.Exit();

If you look in the obj directory, and you don't see your .exe, it's possible that Avast! or other antivirus is deleting it. I would actually see the .exe show up and then disappear. As soon as I turned off Avast!, problem solved.
VS2010 throwing "Could not copy the file "obj\x86\Debug\[file].exe" because it was not found."

The real problem isn't the error you're getting; it's that the application isn't cleaning up after itself.
It's either holding on to references, not freeing resources, or something else that's causing the process to not end when it's being told to close. Fix up that issue and this problem will resolve itself. We can't really help you with that unless you post your code (and at this point, if you need help with that, you should start a new question).

I had to go into windows explorer and delete the bin/debug folder as well as the obj/debug folders. Then I cleaned & rebuilt the project.

Close your project
Delete bin folder
i find it work, :)

Rename the assembly to a different name to solve this issue.

After seeing a similar error in visual studios 2012 out of no where. I have found that that going to the root folder of the project and right clicking on it I unchecked read only and this error went away. Apparently TFS sometimes will made a folder read only. Hopefully this will help anyone with a similar issue. Thanks

This happened to me at VS 2010 and Win 7..
Case :
I can not Rebuild with Debug Configuration manager, but I can rebuild with Release Configuration manager
What I have tried:
Check my account type at control panel - user account --> My Account is Administrator
Set the bin folder not read only
Add security at bin folder to Everyone
stop the iis server
Stop antivirus, check ridiculous running program using task manager and ProcessExplorer
run VS as administrator
If All that way is still not working.
Then, the last way to try:
close solution
close visual studio
start - shutdown
press power button to turn on the computer
login to your account which has administrator previlege at user type
reopen solution
rebuild
that way working. All people call this way as Reset Computer

Mine got solved by:
Clean solution
Close all processes depending on VS (Current instances).
Rebuild

I had same problem, after read your answers , went to Task Manager and searched for app.exe because i believe maybe it doesn't close .
And found it , select it and do END TASK .my problem solved.

Before rebuild the solution, clear the project, stop the IIS and open the "bin" folder property. Uncheck the Read-only Attribute in general tab then rebuild.

I found that ending all msbuild.exe tasks (in Task Manager) fixed the issue with VS2012.

I struggeled with this since years.
I finally downloaded LockHunter to find out who locked the file.
In my case it was MBAM.
Once I added my project's directory to MBAMs exclusion list, I didn't have this problem anymore.

I too had the same issue. I resolved it
Closed my VS, then in Task Manager, End tasks like Microsoft VisualStudio WCF Tools, MSBuild.exe
Then open VS and clean and rebuild.

No matter what the cause of this problem is, the only working solution for me is the following:
Go to Your-Project-Properties -> Application tab(first tab) -> Change the Assembly name.
This way your app creates a new assembly file each time you change the assembly name.
Finally, after you finish to develop, you can delete all those extra assembly files and just keep the last one (main one). Non of the other solutions worked for me, except this one.

Run Visual Studio as Administrator

We recently experienced this on a WinPhone 8 project, in VS 2012 Update 2.
Inexplicably, the cause was using the Tuple type. Removing the code that used a Tuple the problem went away. Add the code back the problem returned.

This will Sound crazy, when ever i build the project the error will be displayed and the avast antivirus will show it as malicious attempt and the project does not run.i just simply disable my antivirus and build my solution again the missing .EXE file has been Created and the project has been successfully executed.
Or you can try this
Visual Studio build fails: unable to copy exe-file from obj\debug to bin\debug

I solved this by killing XDesProc which had a handle on the DLL it couldn't delete.

Well i have the same problem, my way to fix it was to stop and disable the "application experience" service in Windows.

Not a direct answer to your question..
One scenario when this can come is listed below -
If your application is under Debugging process - say by "Attach to Process" debugging, this error may come

If this error was encountered, you can proceed as the following
End the msbuild.exe task
End the explorer.exe task
Run the explorer.exe task again

for me it was the antivirus. Just add visual studio project or entire parent folder to Antivirus exclusion list or you can also add file extension as exclusion and this method worked for me in visual studio 2010/2012

Solution1:
Close the project.
Delete the bin folder.
Open the project.
Build the project.
Solution2:
Add the following code in pre-build event:
attrib -r $(OutDir)*..\* /s
This command line code will remove the ready-only attribute of "bin" folder. Now visual studio can easily delete and copy new dlls.

A very simple solution is to open the Task Manager (CTRL + ALT + DELETE), go to Processes tab and search by name the processes with your project name that are still running. Kill all the processes and go on ! :)

after day with search and build and rebuild i found that you just need to turn off turn on the visual studio its look like it catch the service in different thread

My Visual studio 2019 suddenly stops and restarts and then when i run project this error comes.
I resolve this issue by going into my project folder and delete bin and obj folder
Then clean and rebuild my project. This resolve my issue.

break point is not hitting while debugging

Possible exact duplicates:
Reason for VS.NET ‘current breakpoint will not be hit’ warning?
Why does Visual Studio sometimes not go to my breakpoints?
Why would the debugger not be stopping at a breakpoint in my ASP.NET application?
while debugging,the modified source code the break point is not hitted for a particular aspx page and the following error is shown in the break point
"the break point will not be currently hit.the source code is different from the original version"
but for other page it is working fine.

It worked for me. Try this.
First try rebuilding your project by right mouse click the project > Rebuild If that doesn't work, try a clean of the project (right mouse click on the project > clean)
If that didn't work check this:
1- Right mouse click your project
2- select [Properties]
3- select [Build] tab
4- make sure [Define DEBUG constant] and [Define TRACE constant] are checked
5- Click the [Advanced] button at the bottom of the Build tab page
6- Make sure that [Debug Info:] is set to [full]
7- Click [OK] and rebuild the project ;-)
Hope that works for you! (step 6 generates the .pdb files, these are the debugging symbols)

Some times this occurs if the sourcecode is been copied from the network folder, it messes up the symbol settings. Below solution works for me everytime
In debug mode, select debug->windows->modules
Check your dll symbolStatus . Make sure that it is loaded into
the project (i am sure now the status
is not loaded )
Right click your dll, click symbol settings.
And manually add your symbol path (.pdb file path)
And again right click the dll, and click load symbols
Hope this helps

That suggests the build that's running doesn't match with your code.
Try performing a "clean", make sure that you've stopped any previous debugger sessions etc, then rebuild and retry.

make sure there are not instances of w3wp.exe running. I had several and closing them fixed it for me.

Visual studio repair solved the problem for me
search for visual studio installer in start
select more option for the version you are using and click repair.

In my i changed the connection string but in the browser it was referring to old string so i just did 'empty cache and hard reload in chrome browser' and it worked

This problem occurred to me when I had copied the project. In fact, by opening the old code file if breakPoint is inserted, you will see that it will work. So learn the correct copying method.